What is indicated by the use of purple on a USGS Topographic map?

• A. New roads
• B. Photorevisions
• C. Contoured terrain
• D. Land ownership changes

Answer: (B)

The use of purple on a USGS Topographic map indicates photorevisions. This color is specifically employed to denote features that have been updated through aerial photography, suggesting that the information may have been recently changed or amended based on new imagery. Recognizing this can be crucial for those engaged in navigation, planning, or surveying, as it points to the most current landscape developments such as new structures or changes in terrain that have occurred since the last map version was printed in other colors. The awareness of photorevisions can greatly enhance accuracy in tasks related to land navigation and fieldwork, as it reflects the latest geographical alterations not previously documented in the earlier map editions.